This invention relates to high speed rotary knives which are adapted in operation to rotate adjacent to perforated plates for severing foodstuff projecting from the plate perforations, especially knives which are employed in machines for comminuting foodstuffs. More particularly, the invention relates to such a knife having improved structure for mounting a blade thereof, which structure is adapted for automatic leveling of the blade with respect to an adjacent plate, and to a blade insert assembly for the knife.
Comminuting machines, such as disclosed in U.S. Pat. No. 3,304,976, are used for producing comminuted comestible products, including agricultural and animal products, particularly meat products, for making emulsions for sausages and the like. The machines include one or more high speed rotary knives, the knives being arranged in series when a plurality is employed, to produce a finer textured product, such as a meat emulsion.
In operation, the knives rotate adjacent to perforated plates, also referred to as valve plates, for severing foodstuff which has been propelled partly into and projects upstream from the plate perforations. The knives include blades which traverse the plates with cutting edges on the blades disposed on or against the upstream surfaces of the plates, to sever the foodstuff at the edges of the perforations.
In the type of knife with which the present invention is concerned, the knife includes a holder component which defines an arcuate-bottom slot adapted to receive a blade having an arcuate base seated therein, with the base at the bottom of the slot and conforming thereto, the blade so received being adjustable on the holder component by rotational sliding movement on its base, for leveling a cutting edge on the blade with respect to an adjacent plate. At the start of a conventional operation, the knives with blades therein are laid on the plates, or a jig is used, to level the cutting edges of the knife blades with respect to the plates. Set screws in threaded engagement with the holder components of the knives are tightened into engagement with the sides of the blades mounted in the slots, there being provided an indentation or a dimple on one side of each blade for engagement with a pointed inner end of a set screw. The pointed ends of the set screws mushroom in the indentations upon tightening, and fix the blades rigidly in place.
Despite care in fixing the knife blades in place, they have a tendency to move out of line. In such event, it is necessary to grind down the cutting edge of each nonaligned blade, which wastes expensive steel and shortens the useful life of the blade before operation even commences. Also, labor is required for the mounting and grinding operations.
The comminuting machines are operated with their knives rotating at high speeds, for example, at speeds on the order of 3,000 rpm. The knife blades extend over the perforated plates generally in radial directions from the axes of rotation of the knives. Consequently, the fixed blades and the plates wear unevenly, the wear increasing with increasing distance from the axis of rotation. Spaces may develop between the outer portions of the blades and the plates, smearing meat rather than cutting it cleanly, and/or the inner portions of the blades may gouge into the plates, to increase the wear and create undesirable heat in the product.
Under the most common conditions, the blades wear down and are removed and replaced after several hours of operation, for example. Each time the blades are replaced, they must be leveled and possibly ground to match the plates, with accompanying labor, wasted material, and shortened useful blade life. The worn perforated plates may be sharpened daily. Currently, titanium carbide-coated perforated plates are being introduced, and they materially reduce the wear and increase the useful life of the plates.